Monitoring device for computers with connected peripherals such as monitors, printers or the like

ABSTRACT

The present invention relates to a monitoring device for computers with connected peripherals such as monitors, printers or the like, wherein all peripherals are respectively connected with the computer by at least one ground line. At that, each ground line includes a sensor device looped in between the peripheral and the computer for monitoring a continuous ground connection, and an alarm device actuated by the sensor device, when a deviation is recorded, for signaling an interrupted ground connection. Thereby, a simple and operationally reliable monitoring of one or more computers with connected peripherals is achieved.

The invention relates to a monitoring device for computers withconnected peripherals such as monitors, printers and the like, whereinall peripherals are connected with the computer by at least one groundline.

One such monitoring device is disclosed in DE-GM 91 10 174. In thismonitoring device, which is called an anti-theft device, there areprovided a light signal emitted transmitter and a receiver associatedwith the light signal transmitter for receiving the light signalsemitting by the transmitter. In addition, a light waveguide, whichconnects the transmitter and the receiver and is formed as a lockingelement, is provided. The light waveguide is formed of several partsreleasably connected with each other with couplings and countercouplings. In this way, a plurality of apparatuses such as computerswith connected monitors, printers and the like can be connected witheach other with a light waveguide formed as a locking element, i.e.,they become interlinked and, thus, protected against theft. Thus, assoon the multi-part light waveguide is interrupted by an unauthorizedrelease of a coupling from its counterpart or is manipulated in asimilar way, no signal or a changed light signal is transmitted from thetransmitter to the receiver. A computer anti-theft device with a sensorunit, which includes a computer side and stationary sensor devicesoperationally electrically connected with each other, is disclosed inDE-GM 93 11034. The stationary sensor device is advantageously formed asconduit having, on one side, a contact point and, on the other side, aloop wound around a stationary part, e.g., a desk leg or a shelf rail.The severing of the conductor, loosening of the plug connection or thelike generate an alarm signal.

The known devices are adapted more or less only to monitoring computers,while the conventionally connected peripherals such as monitors,printers or the like are not monitored and can be sealed (please see DEGM 93 11 034). On the other side, the known conventional monitoringdevices formed as multi-part light waveguide locking elements arevery-expensive. Here lies the invention.

U.S. Pat. No. 3,423,747 discloses a monitoring device for, e.g., aTV-set in which each ground line between a respective peripheral and,e.g., the TV-set has a looped-in common sensor device for monitoring thecontinuous ground connection. The sensor device is set for recordingdeviations of an electrical potential from a ground potential at arespective looped-in end of the sensor device. There is provided analarm device, which is actuated by a sensor device upon recording of adeviation, for signaling ground connection interruption.

The subject of the invention is a monitoring device of the typedescribed in the beginning which is simple and operationally reliable.

This object is achieved by a monitoring device having features of claim1.

These features of the invention insure a simple and operationallyreliable construction of the monitoring device because the invention isbased on already available connections between the computer and usuallyconnected therewith peripherals-such as monitors, printers and the like.Each such connection necessarily includes a ground line. The inventionrecognized that a computer with a connected peripheral can be monitoredby monitoring the ground connection between the computer and theperipheral. This is effected with a sensor device looped in between thecomputer and the peripheral for monitoring a continuous groundconnection therebetween. In this way, monitoring can be effected withoutany interference with the peripheral and without disturbing itsfunction. Simultaneously, the monitoring device can be used even withany type of a peripheral and a computer. Overall, neither the operationof the computer nor that of a peripheral is disturbed because themeasured ground connection does not have any active potential and,consequently, no disturbance in the data flow between the peripherals orbetween the computer and the peripherals occurs. The sensor device isset for recording, i.e., for measuring and/or storing (staging) of thedeviations of the operation of the computer nor that of a peripheral isdisturbed because the measured ground connection does not have anyactive potential and, consequently, no disturbance in the data flowbetween the peripherals or between the computer and the peripheralsoccurs. The sensor device is set for recording, i.e., for measuringand/or storing (staging) of the deviations of the electrical potentialfrom a ground potential at a respective looped-in end of the sensordevice. In this way, a successful monitoring can take place even if theconnection between the sensor device and the alarm device is disturbed.In any case, a reliable monitoring of one or several computers withrespective connected peripherals in a simple and operationally reliablemanner becomes possible.

The further important features of the invention will be discussedbellow. Advantageously, the sensor device is formed as a plug-in couplerprovided between the computer and a respective peripheral, e.g., as aplug adapter pin up on an associated output of the computer. Here, theinvention is based on a knowledge that the monitored computer isgenerally connected with the connectable peripheral by a standard cable,so that respective endside and peripheral side standard plug and socketwith a standard number of poles (e.g. 9-, 15-, 25-, etc. poles) are usedfor a series or parallel data transmission. In any case, there exists apossibility to form the sensor device as a plug adaptor between thecomputer and the connecting cable for the connectable peripheral. Thesensor device is advantageously provided at a respective looped-in endwith a computer side input and a peripheral side input, and is set torecord deviations of the ground potential at one input or both inputs.Additionally, there is provided at least one other ground connection,which serves as a reference potential, and an operational voltageconnection for feeding the sensor device with current. There is alsoprovided an output connection leading to the alarm device for signalingan interrupted ground connection. In case the sensor device is formed asa plug adaptor, the output connection to the alarm device is formed as acable leading from the plug adaptor. This multiwire cable can also beused for feeding current to the sensor device via the alarm device. Itis also possible to establish a computer side operational voltageconnection and a ground connection with a connection socket or plugprovided on the computer and a plug adaptor. Independently of this, forproviding a network-independent power supply, an accumulator, which isbuffered during the operation of the computer, can be provided. Thisaccumulator, naturally a plurality of accumulators can be provided, canbe arranged e.g., together with the alarm device in the same housing. Inthis case, the power supply of the sensor device is effected from thathousing. Such a network-independent power supply proved to beadvantageous when monitoring of a computer with connected peripherals isnecessary also with a pulled-out main plug.

Preferably, the sensor device for monitoring a continuous groundconnection comprises an analog idle current loop monitor or a digitalsignal shape monitor of a square wave signal which is communicated to anadditional signal input of the sensor device and phases of which areshifted, in particular, which is negated at a continuous groundconnection. The use of a digital signal shape monitor of a (negated)square wave signal enables to reduce power consumption of the sensordevice by using a CMOS-element. Generally, no alignment of a signalshape monitor is necessary, and no displacement of the operating pointsdue to a temperature drift occurs, so that a continuous groundconnection can be definitely ascertain independently therefrom. Both theidle current loop monitor and the signal monitor can be incorporated inthe plug adaptor when the sensor device is not any more accessible. Itis particularly the case, when the plug adaptor has a cast sheathing andcannot be open. In any case, manipulation of the sensor device issuccessfully prevented. This applies also to the alarm device when it isformed as an alarm card insertable into a computer and has an adjustableduration. Then, the alarm device with a closed computer housing is alsounaccessible. The data flow between the computer and separateperipherals and between separate peripherals is not affected by thealarm card because the alarm card cooperates with the power supply andground contacts and not with data or control contacts when inserted intothe computer. If no free slot is available, the alarm device can bearranged in an external housing. In this case, the alarm device can bemonitored from a location remote from the computer and connectedtherewith peripherals and be connected with the sensor device, e.g., bya telephone line. A connection of an alarm device, which is integratedinto an already available alarm unit, with a sensor device without acable is also possible. In all cases, a TV monitoring of a computer withconnected peripherals is possible when sensor and alarm devices areconnected by a telephone line or without a cable.

For actuation or deactuation of the alarm device, an operational deviceis provided. In the simplest case, it is preferably formed as akey-operated switch, with a LED, if necessary, for displaying the switchposition. Such an operational device or element can be used formonitoring a computer with connected peripherals. If a plurality ofcomputers with connected peripherals, i.e., an entire bureau complexshould be monitored, an operational device, which is formed as aprogrammable operational unit for actuating or deactuating one or morealarm device, is provided. Thereby, targeted separate or a plurality ofalarm devices can be addressed, i.e., actuated and deactuated. It isalso possible to divide a plurality of computers which, e.g., areconnected with each other, in separate groups, with a particularoperational unit being associated with each separate group. Generally,with an actuated alarm device, when a ground connection is interruptedbetween a computer and a connected peripheral, both an acoustic and anoptical alarm signal can be generated which, e.g., can then be manuallyturned off.

In addition to monitoring a connection between a computer and aconnected peripheral, the computer itself can be monitored againstopening of the housing, provided the computer has a two-part metalhousing with a ground line between the two housing parts. This takesplace when the ground line has an additional sensor device between thetwo housing parts for monitoring a ground connection therebetween, withthe alarm device being actuated by the additional sensor device forsignaling an interrupted ground connection. Naturally, to this end, alsospring contacts or the like, which are released when the housing isopened, can be used. In case, the computer includes an interchangeablehard disc, this hard disc can also be monitored against an unauthorizedwithdrawal, by monitoring the available ground connection between thecomputer and the hard disc. This is effected by providing in the groundline a looped-in sensor device between the computer and the hard discfor monitoring a continuous ground connection between the computer andthe hard disc. In this case, the alarm device is also actuated and bythis sensor device for signaling an interrupted ground connection. Allin all, the last mentioned measures permit to monitor the computeragainst the opening of its housing and against withdrawal of the harddisc independently of whether the computer is connected or not withperipherals such as monitor, printer and the like. It should beunderstood that other components, such as streamer, CD-ROM disc drive orthe like can be secured, similar to the hard disc, with an inventivemonitoring device.

Below, the invention will be explained in detail with reference to thedrawing showing an exemplary embodiment of the invention. The drawingsshow:

FIG. 1 a monitoring device for a computer with a changeable hard discand with connected monitor and printer;

FIG. 2 a sensor device formed as an idle current loop monitor; and

FIG. 3 a sensor device formed as a signal shape monitor

The drawings show a monitoring device for a computer 1 having achangeable hard disc 2 and connected with a monitor 3 and a printer 4.The peripherals 3 and 4, like the changeable hard disc 2, are connectedwith the computer 1 by a respective ground line 5. Additionally, thereis provided a respective ground connection 6 serving as a referencepotential. Each ground line 5 has a looped-in sensor device 7 providedbetween the peripherals 3, 4 and the computer for monitoring acontinuous ground connection therebetween. The sensor device 7 isprovided for sensing the deviations of the electrical potential at arespective looped-in end of the sensor device 7. There is furtherprovided an alarm device 8, which is actuated by the sensor device 7,for signaling an interruption of the ground connection. In the exemplaryembodiment, the sensor device 7 is formed as a plug adaptor pinned on anassociated output of the computer 1. The sensor device or the plugadapter 7 has, at a respective looped-in end, a computer-side input E₁,and an apparatus-side input E₂, and serves for sensing of deviations ofone or both of inputs E₁ and E₂ from the ground potential. Additionally,there are provided an operating voltage connection 9 for feedingcurrents to the plug adaptor 7, and an output connection 10 with thealarm device 8 for signaling the interruption of the ground connection.The alarm device 8 is formed as an alarm card insertable into thecomputer 1 and having an adjustable alarm duration. To provide themonitoring device 7 with a network-independent current supply, anaccumulator (not shown) is provided on the alarm card. The actuation anddeactuation of the alarm card 8 is effected in the exemplary embodimentwith an operational element 11 which is formed as a key-operated switch.For actuation and deactuation of one or several alarm devices 8, theoperational element 11 can be formed as a programmable operating unit.Such is not shown.

The computer 1 has a two-part metal housing with a ground line 5 betweenthe two housing parts. For monitoring an unauthorized opening of thetwo-part metal housing, this ground line 5 has an additional looped-insensor device 7 provided between the two housing parts for monitoring acontinuous ground connection between the two housing parts, with thealarm card 8 being also actuated by this additional sensor device forsignaling an interrupted ground connection. This, however, is not shown.Additionally or alternatively, a knife switch can be provided on thehousing part or the alarm card 8 which would detect the opening of themetal housing and/or the disablement of the entire computer 1. This is,however, also not shown. The same applies to the additional sensordevice 7, which is looped-in in the ground line 5 between the hard card2 and the computer 1, for monitoring a continuous ground connectiontherebetween. At that, the alarm card is actuated and by this additionalsensor device 7 for signalling an interruption of the ground connection.

Functioning of the sensor device 7, which is formed as an idle currentloop monitor shown in FIG. 2, will be described below. The sensor device7 or the idle current loop monitor includes, next to the computer sideinput E1 and the apparatus side input E₂, an additional groundconnection 6 which serves as a reference potential, an operationalvoltage connection 9 for supplying the sensor device 7 with current, andan output connection 10 to the alarm card 8, which is not shown in FIG.2, for signaling an interrupted ground connection between the input E₁,and the computer 1 and/or the input E₂ and the monitor 3 or the printer4. If both inputs E₁, and E₂ are under the ground potential, i.e, acontinuous ground connection between the computer 1 and the monitor 3 orthe printer 4 exist, then both semiconductors T₁ and T₂ are blocked. Theoutput connection 10 is connected with the operational voltageconnection 9 by a resistance R₅ and has a positive potential, and noalarm is produced by the alarm card 8. When a continuous groundconnection is interrupted, i.e., one of the inputs E₁, and E₂ or bothinputs E₁, and E₂ are not held at the ground potential any more, theneither one of the semiconductors T₁, and T₂ or both semiconductors T₁,and T₂ are actuated. Then, positive potential is applied to a respectivebase of the semiconductor T₁ and T₂ over the resistor R₅ and R₂ or overresistor R₄ and the combination with base protective resistor R₁ and R₃.The output connection 6 is supplied with the ground potential in asimilar manner. The alarm card recognizes the change of the potentialfrom the operational voltage potential to the ground potential andgenerates a corresponding alarm. A similar effect takes place when theoperational voltage connection is interrupted. Then, also in this case,a ground potential is applied to the output connection 10, and the alarmcard is actuated.

FIG. 3 shows another type of a sensor device 7 formed as a signal shapemonitor of a square wave signal which is fed to an additional input 12of the sensor device 7 and which is negated at a continuous groundconnection. The functioning will be explained below.

The core element of the signal shape monitor are three controlledswitches A, B and C which are commercially available as an integratedswitching circuit. When both inputs E₁, and E₂ are under the groundpotential, i.e., a continuous ground connection exists between thecomputer 1 and the monitor 3 and the printer 4, the control inputs ofthe switches A and B are likewise under the ground potential, and bothswitches A and B, as shown are open. The square wave signal, which isfed over the additional signal input 12₁ controls then, over theresistor R₃, the control input of the switch C, which opens and closes,and transmits a negated square wave signal over the output connection 10to the alarm card 8. In this case, no alarm is produced. As soon as oneof the inputs E₁ and E₂ are not at the ground potential anymore, i.e., acontinuous ground connection between the computer, and the monitor 3 orthe printer 4 does not exist, the switch A and/or B is closed becauseits control input receives a positive potential from the operationalvoltage connection over the resistance R₁, R₂. As soon as one or bothswitches A and B are closed, the switch C also becomes closed and doesnot open or close in accordance with the square wave signal alteration.Consequently, the output connection 10 receives a ground potential, andthe alarm card 8 produces an alarm.

The opposite phase position of the square wave signal, which is fed viathe input side to the additional signal input 12 opposite to the outputside square wave signal, which is transmitted via the output connection10 to the alarm card 8 at the continuous ground connection, preventsfaking of a continuous ground connection by manipulating the outputconnection 10.

The negated square wave signal can be negated again by furthermanipulation so that it can be verified whether the input side squarewave signal correspond to the (twice negated) output signal.

I claim:
 1. A device for monitoring a ground connection between acomputer and a peripheral connected by at least one ground line, themonitoring device comprising:a sensor device to be looped into the atleast one ground line for monitoring a continuous ground connectionbetween the computer and peripheral, the sensor device having twolooped-in ends associated with the computer and the peripheral,respectively, and serving for sensing deviations of an electricalpotential at a respective looped-in end from a ground potential, and thesensor device further having a reference end connected with anadditional ground line extending between the computer and the peripheralfor providing a reference potential; and an alarm device connected withthe sensor device for generating an alarm signal of a broken groundconnection in response to the sensor device sensing a deviation of theelectrical potential from the reference potential.
 2. The monitoringdevice according to claim 1, wherein the sensor device is formed as anadapter plug attachable to a respective computer output.
 3. Themonitoring device according to claim 1, wherein the sensor devicecomprises three inputs defining, respectively, the two looped-in endsand the reference end, and an output connected with the alarm device;and wherein the monitoring device further comprises voltage means forsupplying power to the sensor device.
 4. The monitoring device accordingto claim 3, wherein the voltage means comprises a battery.
 5. Themonitoring device according to claim 1, wherein the sensor devicecomprises one of a closed circuit loop monitor and a signal form monitorfor monitoring a square wave signal supplied to at least one of twoinputs defining the two looped-in ends.
 6. The monitoring deviceaccording to claim 1, wherein the alarm device comprises an alarm insertcard adapted to be plugged into the computer and having an adjustablealarm duration.
 7. The monitoring device according to claim 1, furthercomprising a control device for activating and deactivating the alarmdevice.
 8. The monitoring device according to claim 7, wherein thecontrol device comprises a key-operated switch.